I was gonna say yes and no. On my ECB, yes, it smothers bad like others said. On the SnP, no, the grate is high enough that I can go 12 or so hours without ash buildup problems. Much like steve, I occasionally do take a stick and shuffle coals to clump them together.
EDIT: Dude, I drilled holes in the bottom of my ECB. Go bigger than 1/4 inch for sure. That's what mine are and they need to be bigger, I think 1/2 inch may even be a bit small, but you can always make them bigger.